A win would over their fellow strugglers would have secured Gate’s premier division status but they now stand one place above the drop zone and could still be caught by third-bottom New Mills, who are seven points behind with three to play.
All the goals came in the second-half, the damage done when Gate conceded three in 10 minutes.
Manager Danny Penswick made four changes to the side narrowly beaten by Ashton Athletic on Sunday as defender Paul Alexander started up front, with Paul Carroll, Mark Thornber and Ben Seear all coming into the side.
Neither team could convert their chances in a tight first half, Andrew Richards blocking a Darwen shot before Ben Seear fired wide from outside the box at the other end.
The best chance of the half fell to the hosts, when Gate switched off at a throw and were lucky to see a header flash wide. Gate had a chance of their own before the break but Corey Moorhead’s shot at the back-post was blocked for a corner.
The major turning point arrived 10 minutes into the second half, when Tarren Moxon’s header for Gate was cleared off the line and Darwen raced to the other end to break the deadlock. A break down the right and a low cross was finished by Nick Hepple.
The second followed five minutes later, when Conor Gaul was allowed too much space to cross from the bye-line for Bobby Langford to tap in at the near post.
And it was 3-0 on 65 minutes, when Hepple fired home his second from outside the box. Gate pulled one back on 72 minutes, when substitute Brett Dawson cleverly beat the keeper one-on-one.
But two minutes later, Hepple sealed his hat-trick and virtually secured Darwen’s safety.
Gate, however, remain anxious to win one of their remaining two games. They face third-placed Runcorn Linnets in Saturday’s final home game of the season.
Gate: Griffith, Richards, Carroll, Moorhead, Penswick, Casey, Hall, Thornber, B.Seear, Alexander, Moxon. Subs: Noblet, Dawson, Smith, Seear.